JP2004537650A - Apparatus for electrodeposition of aluminum or aluminum alloys from organometallic electrolytes containing alkylaluminum - Google Patents

Abstract

A device for the galvanic precipitation of aluminum and/or its alloys, from electrolytes containing metal organic aluminum alkyl complexes, comprises a carrier frame with a support and transport members, a galvanizing drum, a drive unit(s) for the drum, and drum carrier arm(s). The drum comprises a material resistant to aqueous and metal organic electrolytes at temperatures up to 110 degrees C. <??>A device for the galvanic precipitation of aluminum and/or its alloys, from electrolytes containing metal organic aluminum alkyl complexes, comprises a carrier frame with a support and transport members, a galvanizing drum, a drive unit(s) for the drum, and drum carrier arm(s). The drive unit (3) is in an encapsulated gas-tight housing. The drum (13) has a perforated inner pipe (15) along its longitudinal axis, which has a side opening opposite the electrolyte feed in the electrolyte container. The drum comprises a material resistant to aqueous and metal organic electrolytes at temperatures up to 110 degrees C.

Description

【Technical field】
[0001]
The present invention relates to an apparatus for electrodeposition of aluminum or aluminum alloy from an organometallic electrolyte containing alkylaluminum, comprising a support frame having a stand and a transport bearing, at least one plating barrel, Device comprising at least one drive unit for a plating barrel, and one or more holding arms for a plating barrel.
[0002]
Electroplating of small portions and bulk materials in aqueous solutions, such as nickel plating or zinc plating, is usually performed in a rotating perforated barrel made of polyethylene or polypropylene. These barrels are driven by electric motors located in a plastic housing in a support rack. To prevent undesirable metal epitaxial growth, current transfer to the article is primarily provided by a flexible copper cord placed laterally on the barrel and covered by a plasticized PVC tube.
[0003]
Electrodeposition of aluminum or aluminum alloy from aqueous solutions is not possible due to the very low potential of aluminum. Therefore, electrodeposition must be performed from a non-aqueous organic system. In particular, electrolytes containing alkylaluminum, usually using organic solvents, are used for this purpose. Thus, deposition of fine crystalline aluminum and aluminum alloy layers is well achieved from anhydrous alkylorganoaluminum electrolyte systems, where the alkyl aluminum complex is dissolved in an aromatic hydrocarbon such as toluene. .
[0004]
However, a plating barrel used in water-based electroplating cannot be used in an organic electrolyte solution. This relates to the organic solvent used and the operating temperature at which such electroplating takes place, between 90 and 100C. At such temperatures, and in the corresponding organic solvents, conventional aqueous barrels are not stable and decompose or dissolve, which can contaminate the electrolyte. Furthermore, there is a risk of barrel distortion such that mechanical stability is no longer guaranteed.
[0005]
Also, electroplating systems for bulk materials used in organic media, in particular for depositing aluminum, are known from the prior art. However, these systems did not have general utility.
[0006]
This further includes the prior art described in EP 0042503 A1. It describes an apparatus for electrodepositing aluminum from an organic electrolyte. SUMMARY OF THE INVENTION It is an object of the invention to create an apparatus that does not require the plating barrel to be removed from the plating bath for loading and unloading. The above prior art describes the use of a vehicle for the part to be coated. It is used to fill the plating barrel, extends through the gate into the plating bath, and stops on a closable opening in the plating barrel. The barrel is openable and closable from the outside and is provided with a drainage container that can be exposed to an inert gas and an inert fluid to empty the barrel. It is located below the plating bath and is connected to it by a closable tubular connecting element.
[0007]
The prior art described above shows a plating barrel of very complex configuration, which also has no general utility.
[0008]
The present invention is an apparatus for electrodepositing aluminum from an organic electrolyte system, wherein the plating barrel is modified to be stable in the medium used and at the applied temperature, and in a flammable medium. It is based on the object of providing a device having a safe drive and nevertheless capable of producing high quality coatings with aluminum or its alloys.
[0009]
Said purpose is a device in which the drive unit 3 is arranged in a hermetically sealed airtight housing, the plating barrel 13 is arranged along its longitudinal axis and has an inner tube 15 open on its side, comprising: Is disposed at a position directly opposite to the electrolytic solution supply section in the electrolytic solution container, and the plating barrel 13 has a temperature up to 110 ° C., in either the aqueous electrolytic solution or the organometallic electrolytic solution. Is also achieved by devices made of stable materials.
[0010]
By enclosing the drive unit in an airtight housing, operation of the barrel in flammable liquid is much safer. The case is preferably made of stainless steel and the drive shaft for the barrel is guided through the housing wall by a hermetic shaft guide with sealing (preferably made of polytetrafluoroethylene).
[0011]
To protect the drive motor and as a further measure of protection against the infiltration of flammable organic solvents, the housing case is filled with an inert gas such as nitrogen or argon, preferably of 0.1 to 0.3 bar. Apply excessive pressure. The housing also includes a supply valve and an overpressure blow valve with a nonreturn flap.
[0012]
At each filling / unloading step, an inert gas at a pressure of about 0.1 to 0.2 bar above the setting of the blow-off valve is automatically supplied through the supply valve into the drive unit housing on the station. After each coating step, the inert gas atmosphere in the drive unit housing is purged, and after each cycle, the excess pressure in the housing is reset. The purge time and the inert purge gas amount are set by the plant control means.
[0013]
Another problem with plating barrels known from the prior art is the stability of the barrel material. In long-term operation, conventional barrel materials such as polyethylene and polypropylene are not stable in the organic solvents used in aluminum coatings. This problem is solved by using suitable plastics reinforced by glass fibers which are insoluble in organic solvents. In a preferred embodiment, the plating barrel is made from glass fiber reinforced polyphenylene sulfide containing at least a proportion of glass fibers of at least 40%. This guarantees the chemical stability of the plating barrel at operating temperatures in the electrolyte up to 110 ° C., as well as the wear resistance.
[0014]
In a preferred embodiment, the drive gears are made of the same material. Another advantage is that the material is also stable in dilute acids and bases, so that pretreatment and secondary treatment of the parts to be electroplated can be carried out in aqueous systems such as acids and / or bases without migration. What can be done in the same barrel.
[0015]
Providing an inner tube with an open plating barrel improves circulation of the electrolyte. Electrolyte circulation plays a very important role in the electrodeposition of metals from organic electrolytes. Because the solubility of the organometallic complex is limited, if the circulation of the electrolytic solution is insufficient, shortage of metal ions may occur immediately in the liquid boundary layer near the product. This also leads to a deterioration of the quality of the coating of the material, in particular the burning of the material to be coated, the rough and uneven layers and possibly also the decomposition of the electrolyte. In particular, this problem occurs in the precipitation of aluminum alloys, but is also observed in the deposition of pure aluminum. To circumvent this problem, the apparatus of the present invention includes an open inner tube arranged along the longitudinal axis of the plating barrel and having a lateral opening facing the container wall of the electrolyte container. , Provided in the barrel. When the device of the present invention is placed in an electrolytic cell, the lateral opening of the inner tube is located in the container wall at a position directly opposite the electrolyte supply line. Thus, during coating, the fresh electrolyte is passed through the inner tube at high speed directly to the substrate, ensuring a good replacement and preventing the above-mentioned problems from occurring. In a preferred embodiment, an additional auxiliary anode can be placed in the inner tube, which can further increase the local concentration of metal ions and increase the coating rate.
[0016]
According to the prior art, the holding arms of conventional barrels are mainly coated with rubber and are therefore unstable in organic electrolysis cells. This also applies to the usual PVC jacket of the conductor tracks for the electrolyte current. With such an apparatus, it is expected that the metal will grow epitaxially on the power supply bar. According to the invention, this problem is solved by a hollow body holding arm made of steel and having a core of polyphenylene sulfide. A power supply bar for supplying electrolysis power is disposed in the core of the insulating material. It is only in the barrel where the power supply bar in the product in the bearing of the holding arm and the contact bulb are connected. With this type of configuration, further protection of the power supply bar against unwanted metal epitaxial growth is no longer necessary. The holding arm itself has no applied potential and is further externalized by a plastic layer (preferably made of PVDF (polyvinylidene fluoride) or ethylene and chlorotrifluoroethylene based thermoplastic fluorocarbons) coated thereon. Is protected.
[0017]
The present invention is described in more detail with reference to FIG. 1 below. Reference numeral 1 indicates a support frame having a stand including a single element of the apparatus, a plating barrel, a drive unit, and a holding arm. The support frame has transport bearings 4 disposed thereon, which are used to sink or lift the device into or out of each electrolyte or rinsing bath.
[0018]
The support frame has a drive motor 3 enclosed therein, which is suspended so as to be electrically insulated and has an airtight shaft guide 5. The drive gear 6, preferably made of polyphenylene sulfide, is located at the end of the shaft. The drive gear drives a plating barrel 13, which is preferably made of glass fiber reinforced polyphenylene sulfide. The plating barrel 13 is connected to the support frame 1 by the holding arm 11. The holding arms 11 are preferably made of stainless steel, they are hollow and the outside is coated with a fluoropolymer. The hollow of the holding arm 11 contains an insulating material, in which power supply bars 9, 10 for supplying electrolysis power are arranged. Reference numeral 12 indicates a bearing block for a plating barrel. The plating barrel has a perforated side wall 14 and an inner tube 15 open to that side. To increase the electrolyte concentration near the material to be coated, an internal auxiliary anode 17 can be introduced into the barrel through this tube. Numeral 18 indicates a pick-up contact, preferably made of copper, arranged in the barrel.
[0019]
Further, a flexible current carrying contact 16 is located inside the plating barrel.
[0020]
Numeral 9 indicates a power supply line for the material to be coated. The line is insulated inside the barrel holder. Reference numeral 7 denotes an inert gas vent of the drive unit housing including the non-return flap.
[0021]
By using the apparatus of the present invention, high quality coatings of aluminum or aluminum alloys can be produced. Coatings of magnesium and magnesium alloys are also possible. In that case, the corresponding alkyl magnesium-containing electrolyte is used. The device of the present invention is wear resistant and can be used in aqueous systems, for example, in rinsing processes.
[0022]
Reference list 1 Stand 2 Power supply bar 3 Sealed drive motor with electrically insulated suspension 4 Transport bearing 5 Hermetic shaft guide 6 Drive gear 7 Inert gas vent in motor housing with non-return flap 8 Inert gas purge valve 9 Power supply line for the material to be coated insulated inside the barrel holder 10 Insulating material 11 inside the holder 11 Stainless steel coated outside with PVDF / Halar Barrel holder 12 Bearing block 13 for barrel 13 Glass fiber reinforced PPS barrel 14 Perforated side wall 15 Open inner tube 16 Flexible current transfer contact 17 Internal auxiliary anode 18 Pickup contact [Brief description of drawings]
[0023]
FIG. 1 shows one embodiment of the device of the present invention.

Claims (8)

Apparatus for electrodepositing aluminum and / or aluminum alloy from a metalorganic electrolyte containing an alkylaluminum complex on a material to be coated, comprising a support frame having a stand and a transport bearing, at least one for plating A barrel, at least one drive unit for the plating barrel, and one or more holding arms for the plating barrel;
A drive unit (3) is arranged in the hermetically sealed airtight housing;
The plating barrel (13) is arranged along its longitudinal axis so that the lateral opening is arranged at a position directly opposite to the electrolytic solution supply section in the electrolytic solution container, and the inner tube (13) opened to the side. 15),
The apparatus according to claim 1, characterized in that the plating barrel (13) is made of a material that is stable in both aqueous and organometallic electrolytes at temperatures up to 110C. Device according to claim 1, characterized in that the plating barrel (13) consists of polyphenylene sulfide reinforced by at least 40% by weight of glass fibers. Device according to claim 1 or 2, characterized in that the drive unit (3) comprises an automatic purge pressurizing device for inert gas. 4. The device according to claim 1, wherein an auxiliary anode (17) is arranged in the inner tube (15) to increase the concentration of metal ions. 5. The drive unit according to claim 1, wherein the drive unit has a drive shaft guided through a housing wall of the drive unit by an airtight shaft guide made of polytetrafluoroethylene. apparatus. 6. The device according to claim 1, wherein the holding arm is a hollow body made of steel and is provided with a core made of polyphenylene sulfide. 7. The device according to claim 1, wherein the holding arm is covered on the outside by a plastic layer of polyvinylidene fluoride or a thermoplastic fluorocarbon based on ethylene and chlorotrifluoroethylene. The device according to claim 6, characterized in that a power supply bar for the electrolysis power supply is arranged in the core of polyphenylene sulfide.

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